Constant reads wouldn't be as hard on the drive, but again, the more the mechanics inside the drive work/move, the more they will wear down. For HDDs, most failures are mechanical failures.
That said, even with a consumer grade drive, I personally wouldn't worry too much about it; modern drives are pretty solid in general, just make sure you backup anything important.
If you're really worried about it, WD's gold line is made for constant reads/writes 24/7 and to be reliable under those conditions